Some clarifications:
1. Under a RIS the pilot is wholly responsible for requesting a controlled airspace joining clearance. (This applies equally to IFR and VFR traffic).
2. All STMA controllers are aware that traffic can enter the TMA VFR - indeed it is a popular oral board question! However, it is an uncommon occurence, something that the more recently valid controllers might not have experienced for real.
3. Although VFR traffic cannot be refused a joining clearance per se, it can be instructed to remain clear of controlled airspace until a convenient time.
4. The southern boundary of Edinburgh's local area (the bit of the TMA delegated to them by Scottish) is about 10nm north of TLA, so traffic joining via TLA in the STMA therefore requires a clearance from Talla Sector.
5. Scottish does not receive VFR flight plans.
6. I can't speak for this specific occurence, but Scottish will always provide the best service possible, dependent on workload, and that certainly includes VFR joiners inbound to Cumbernauld.
There seem to be a lot of NATS bashers out there, but the truth is that 99% of our controllers are committed to provide the best service possible to all our customers, whether VFR, IFR, commercial or GA. It is pressure of work and the over-riding priority to manage traffic safely at all times that will determine how accomodating we can be.